The prior art is replete with various stoppers used to confine materials within test tubes, bottles and other like vials. Conventionally, modern stoppers are made of an elastomeric material that is inserted into the open end of the test tube with an interference fit. The interference fit between the elastomeric stopper and the material of the test tube creates an air impervious seal that isolates the contents of the test tube from the surrounding environment. The further the elastomeric stopper is advanced within a test tube, the larger the area of contact becomes between the elastomeric stopper and the test tube. Consequently, as an elastomeric stopper is advanced into a test tube the more force is required to further advance the stopper or to remove the stopper from the test tube. As an elastomeric stopper is advanced into, or removed from, the open end of a test tube, it is typically twisted as the stopper is pressed downwardly into the test tube or pulled upwardly out of the test tube. The twisting movement applied to the stopper helps overcome the resistance to the desired upward or downward movement caused by the interference fit between the stopper and the test tube. As such, less downward force is required to press the stopper into a test tube if the stopper is twisted as the downward force is applied. Similarly, less upward force is required to pull the stopper from the test tube, provided the stopper is twisted as the upward force is applied.
When forming an elastomeric stopper it is desirable to use an elastomeric material that readily yields when stressed. As such, the stopper will readily deform into the open end of the test tube and form the desired seal. However, using such soft elastomeric materials has certain disadvantages. To advance a stopper into a test tube, or pull a stopper from a test tube, the material of the stopper extending above the test tube must be engaged. As has been explained, the stopper is usually inserted with a pulling force or a pushing force that is coupled with a simultaneous twisting action. As a user engages the stopper with such forces, the soft material of the stopper deforms in the hand of the user. Consequently, it is difficult to maintain a grip on the stopper as the stopper is manipulated into, or out of, a test tube. Similarly, the soft elastomeric materials used in manufacturing conventional stoppers tear easily. As such, the stopper can only be pulled and/or twisted within a limited range of forces before the material of the elastomeric destructively yields. If the force of the interference fit, retaining the stopper within a test tube, is greater than that which can be non-destructively applied to the head of the stopper, then the stopper cannot be removed from the test tube without being permanently damaged. For this reason, the material of elastomeric stoppers, as well as the configuration of the head of the stopper, put limits upon the degree of engagement that can exist between the stopper and the test tube.
Test tubes, bottles and similar vials are often used to contain many highly dangerous or toxic substances. As the test tube is manipulated, the contents of the test tube contaminates the stopper used to close that test tube. Since elastomeric stoppers require a substantial amount of manipulation to be removed from a test tube, it is difficult to prevent a person from contacting the contaminated portions of the stopper. In the prior art, elastomeric stoppers have been manufactured with caps that are configured to fit over the stopper and assist a person in manipulating the stopper. Such caps help isolate the stopper as it is being manipulated, thereby reducing the risk of a person contacting the contaminated stopper. Such a prior art stopper and cap assembly is exemplified in U.S. Pat. No. 4,465,200 to Percarpio, entitled LOW CONTAMINATION CLOSURE FOR BLOOD COLLECTION TUBES. The Percarpio patent, however, does embody some disadvantageous features. In the Percarpio patent, the outer cap is joined to the inner stopper with an interference fit. However, as the cap member is twisted, the stopper may be deformed and the interference fit removed, thereby allowing the outer cap member to turn independently of the inner stopper. Since the cap member does not act to rotate the inner stopper, the stopper may not properly advance into the test tube and therefore may not adequately seal the test tube.
The primary purpose of stoppers is to confine the contents of a test tube within the test tube. However, test tubes are often spun, shaken, heated, cooled or otherwise treated in the course of typical test procedures. Such processing often moves the contents of the test tube against the stopper, and challenges the integrity of the seal created by the stopper. The primary seal created by conventional stoppers, is the interference seal the stopper makes with the inside surface of the test tube. However, to ensure the integrity of the seal, certain prior art stoppers also create a secondary seal on the outside surface of the test tube. As such, the contents of the test tube would have to escape both the primary seal and the secondary seal of the stopper in order to leave the test tube. Such prior art stoppers containing inner primary seals and outer secondary seals are exemplified U.S. Pat. No. Re. 18,669 to Duffy et al., entitled BOTTLE CAP AND STOPPER and U.S. Pat. No. 3,869,059 to Ellis entitled STOPPERS.
In certain applications, such as when the contents of a test tube are to be heat treated, as drying by lyophilization, the stopper of the test tube must be removed to allow the unwanted gases to escape from test tube. Additionally, since the test tube is left open, the probabilities of spillage from the test tube is increased as the test tube is manipulated and its contents processed. Once the contents of the test tube are properly processed, a new stopper is applied to the test tube so as not to contaminate the processed contents of the test tube with the non-processed material left upon the old stopper.
Since a large variety of materials are held within test tubes, it is often required to provide some form of identifying markings on the test tube, thereby enabling different test tubes to be distinguished. Typically, test tubes are identified by a label applied to the test tube or its stopper after the test tubes are filled. This method of labeling test tubes is not ideal because such labels are typically small, the writing on such labels is small and the labels can be easily covered with overflow blood or like materials being held in the test tube. A more efficient manner to identify test tubes is by color coding the stoppers used to cap the test tubes. However, prior art test tube stoppers are typically made of butyl rubber. Butyl rubber is commercially manufactured in only a few colors. As such, creating a large variety of colors in such prior art stoppers adds significantly to the cost at which, such stoppers can be manufactured. Furthermore, prior art stoppers are typically manufactured to be only a single color. As a result, only a small number of stoppers can be manufactured that are clearly distinguishable from one another. If numerous test tubes are to be identified, it is difficult to provide a large enough variety in the colors for the stoppers so that the stoppers are not close in color and shade.
It is therefore, an objective of the present invention, to provide a test tube stopper that can be economically manufactured in a large variety of colors and provides a means to color code the test tube stoppers utilizing multiple color combinations.
It is a further objective, of the present invention, to provide a stopper that can be manipulated to selectively allow gases to exit a test tube without the stopper being removed from the test tube.
It is yet another objective, of the present invention, to provide a elastomeric stopper with an outer cap member that helps in the manipulation of the elastomeric stopper and provides a secondary boundary that helps to prevent any inadvertent escape of materials from the test tube.